The present invention relates to an optical image processor, and more particularly, to an optical image processing system that is capable of providing a highly selectable modulation transfer function.
Typical image information desired to be processed includes real-time X-ray images of internal structures of human bodies. The X-ray images usually have information that is of particular interest, such as blood vessels in the heart, and much additional information that is of little or no interest to an observer, such as a person's rib cage or other bone structures. It would be desirable to process an optical image, such as just described, to eliminate much of the information that is not of interest. This, fortunately, is possible because the different types of material represented in an X-ray image typically have different spatial frequencies. Spatial frequencies are related to the size of objects in an image. Large objects have low spatial frequencies, and small objects have high spatial frequencies.
The degree of optical processing imparted to an image can be expressed in terms of the modulation transfer function of an optical system. One hundred percent modulation represents no change to an image, whereas zero percent modulation represents a complete blockage of all image information.
It would be desirable to provide an optical image processor having a modulation transfer function that is highly selectable. A desirable modulation transfer function of high selectability would be variable nearly continuously between zero and one hundred percent of spatial frequencies, and, further, would be capable of selectively passing a desired range or ranges of spatial frequencies while suppressing other frequencies. Such a system would desirably be compact and utilize a small number of components for economy.